Were Sherlock Holmes a cosmologist, he might have said, "It's filamentary, my dear Watson."
The acute Watson might have argued, however, that it's more like a spider web. And if word of Holmes' theory got around, other big thinkers might have insisted, "No, it's spongy, just like your brain!"
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They'd all have been arguing the same cosmic case: That the early universe contained a series of threads and clumps, not unlike a spider web dappled with water droplets, and that this structure set the stage for the growth of galaxies and galaxy clusters seen today.
Of course, like a good murder mystery, this theory began without much to go on. A small bit of circumstantial evidence here. A wild hunch there.
Now a group of European researchers has done some fine long-distance sleuthing, looking way back in time to when the universe was just 15 percent of its current age, to uncover some vital clues in the case.
Using the European Southern Observatory's Very Large Telescope, they have spotted a string of dense clumps of hydrogen, which glow because inside them a few hot young stars are forming. The clumps are galaxies-to-be, or protogalaxies, the researchers say. And they were found to lie within a tubular region of space -- a filament -- supporting a popular theory of the cosmic web, involving filaments stuffed with protogalaxies.
"This discovery certainly bolsters the concept of the cosmic web," said Lev Kofman, professor of the Canadian Institute for Theoretical Astrophysics.
Kofman, who was not involved in the study, added that more research would be needed before alternative models of galaxy formation could be ruled out.
Fatal attraction
The most widely accepted models of the early universe now hinge on a discovery from the early 1990s. A satellite called the Cosmic Background Explorer (COBE) was observing a pervasive feature of the universe called cosmic microwave background, or CMB, which was emitted shortly after the Big Bang.
Since its discovery in 1965, the CMB had appeared to be a uniform temperature in every direction of space. But COBE found tiny variations, lumps and bumps that researchers now believe were seeds of structure. Computer models see these variations as leading to the first large-scale architectural components of the universe -- long filaments connected at nodes. The spider web.
Clumps of hydrogen -- think of them as the drops on the spider web -- developed along these filaments. Each would have had mass, gravity and some random velocity, the computer modelers say. And they would have streamed along the filaments toward the nodes.
"Sometimes this random motion will cause two protogalaxies to pass so close to each other that they will experience fatal attraction," explained ESO researcher Palle Møller. "They will fall into each other."
Repeating the process many times, larger and larger galaxies would have formed. Over billions of years, the filaments were replaced by large clusters of galaxies connected by bridges -- the remains of the largest of the original filaments. Galactic collisions continue today.
Next page: Ancient pop art, and a truly cosmic thought
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